Type II restriction endonucleases are endodeoxyribonucleases which are able to recognize and cleave DNA at site-specific sequences. The ability to specifically cleave DNA into discrete fragments is essential for the manipulation of DNA. Type II restriction endonucleases are thus of value for the analysis of DNA molecules.
Although Type II restriction endonucleases are known which are specific for numerous DNA sequences, there is still a need for further type II restriction endonucleases which are specific for DNA sequences that up to now have not been recognized by any of the known restriction endonucleases. Further, the use of restriction endonucleases whose recognition sites contain a large number of base pairs are of particular interest since fewer, larger fragments of DNA are likely to be generated by treatment with such restriction endonucleases. However, most of the restriction endonucleases known recognize a sequence of four to six base pairs, and hence the number of cleavage sites is too great when manipulating DNA, making its analysis difficult in many cases. Thus, there is a demand for restriction endonucleases capable of recognizing a sequence of more than 4 or 6 base pairs.